JP4209385B2 - Piston for internal combustion engine - Google Patents

Description

  The present invention relates to a piston for an internal combustion engine according to claim 1.

  Such a type of piston is known, for example, from DE 2647250 or DE 4000846. In these pistons, the mounting surface of the expansion sleeve and the mounting surface of the piston, where the expansion sleeve and the piston are in contact, are slightly inclined with respect to the plane that normally extends with respect to the longitudinal axis of the piston. Yes. In this case, the inclination of the receiving surface on the piston side has only a machining technical advantage and is therefore increased to the extent necessary to achieve good machining. In this case, the inclination is obtained by means of an annular ball segment. This section transitions via a different transition radius to the wall of the hole provided for each expansion sleeve. When the piston-side receiving surface is formed in a concave shape, the mounting surface of each associated expansion sleeve is formed in a corresponding convex shape. In this case, the curvature of both mounting surfaces is different when an annular gap is formed between the mounting surfaces that extends outward in the cold state. The size of the annular gap is designed to contact without gaps when tightened under equal preload.

In German Patent No. 2647 2 50, in order to prevent overloading of the inner region of the hole, ie specifically the inner edge of the mounting surface for the expansion sleeve, the circular shape of the expansion sleeve It is proposed that the center of curvature of the convex mounting surface be provided next to the longitudinal axis of the expansion sleeve, unlike the radius of curvature of the concave counterpart surface under the piston. Thereby, the first contact portion between the expansion sleeve and the piston lower portion is obtained in the central range of the mounting surface between the expansion sleeve and the piston lower portion when viewed in the radial direction. When the screw is tightened, the mounting surfaces facing each other obtain complete contact from the center first contact line.

  In the configuration according to DE 4000846, the mounting surface of the piston for the expansion sleeve transitions tangentially through the radius of curvature R1 to the peripheral surface of the hole with the expansion sleeve. The value of the radius of curvature R1 is larger than the difference between the radius of the hole and the radius of the inner circumference of the expansion sleeve mounting surface on the piston side. As a result, the larger overall inclination of the mounting surface between the expansion sleeve and the corresponding bearing part of the piston results in a larger force transmission surface between the expansion sleeve and the corresponding bearing part on the piston side. Obtained at a predetermined diameter of the hole containing the

  With this arrangement, in the clamped state, the contact force between a predetermined range of the mounting surface is approximately equal in magnitude, however, this range is still very close to the edge of the receiving hole of the expansion sleeve. This does not eliminate the risk of stress cracking due to piston overload.

  Therefore, the object of the present invention is to improve the piston of the type described at the beginning, which can be easily manufactured, and an improved force introduction from the connecting piston member to the piston can be achieved compared to the prior art. Is to provide what to do.

  This problem is solved by the features of claim 1.

  The basic advantage lies in the precisely defined contact range of the mounting surface between the pressing member and the corresponding bearing part of the piston. As a result, force can be introduced into the lower part of the piston without cracking or deformation of the piston. Especially when tightening the expansion screw, the gap between the pressing member and the mounting surface is closed from the radially outer side to the inner side as measured by the piston diameter, thereby accommodating the pressing member present at the lower part of the piston The hole is unloaded. Thereby, plastic deformation is almost eliminated. Similarly, the loading range of the mounting surface of the hole for accommodating the pressing member from the elliptical part to the cylindrical part is decisively released by the lever action with reduced contact force.

  Embodiments of the invention will now be described with reference to the drawings.

The piston lower part 1 has a hole 4 with a hole axis or an expansion screw axis 3. This is the hole 4, which is shaped in the form of a sphere, the pressing member 2 with rests surface 6 with a radius r _k are located. The hole itself has a radius a and is formed in the shape of an elongated spheroid with a large half-axis c according to the formula of claim 1 in the end range as viewed in the direction of the spatial coordinate z. . In this case, the coordinate axis z of the elongated spheroid coincides with the axis 3 of the hole for accommodating the pressing member 2. Accordingly, in accordance with the design suitable for the size of the mounting surface, in a state where the mounting surface is not tightened, the spherical mounting surface 6 of the pressing member 2 and the elliptical mounting of the holes provided in the piston 1 The surface 5 is in contact with the point indicated by reference numeral 7. These points 7 are located very close to the hole diameter toward the outside in the radial direction. By tightening the expansion screw, these points 7 move radially inward along the elliptical mounting surface 5 until the gap is closed. Thereby, an optimal force introduction into the lower part of the piston is obtained without crack formation or plastic deformation in the piston.

It is a cross-sectional view which shows the press member which reached | attained in the accommodation hole of a piston.

FIG. 5 shows the device / configuration of the mounting surface according to the invention below the piston.

2 is a detailed cross-sectional view of the mounting surface according to FIG.

Claims (1)

A piston for an internal combustion engine, comprising: a lower part that forms an axial range; and a piston upper part that is coupled to the lower part via an expansion screw and forms a piston crown and an annular range. The expansion screw provided inside is located on a pressing member that engages with each hole provided in the lower part of the piston, and the respective contacts between the pressing member and the lower part of the piston extend at an angle with each other. In the form that is supposed to be obtained via
The mounting surface of the piston lower part (1) for the pressing member (2) follows the surface of the elongated spheroid of the general formula x ² / a ² + y ² / a ² + z ² / c ² = 1 X, y and z define the spatial axis, and a and c define the half axis by a <c,
The space axis z of the elongated spheroid coincides with the axis of each hole for accommodating the pressing member (2), and the mounting surface of the pressing member (2) has a general formula x ^{2 + y 2} + z ² ₌ follows the surface of a sphere of _r ^{k _2,} characterized in that it is a _r k <a, the piston for an internal combustion engine.

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